This invention relates generally to leak testing and lubrication of sealed joints in the tracks of crawler type equipment and, more particularly, to methods and means for testing the seal integrity of a hollow track joint, followed by insertion of lubricating oil into the joint in a manner which ensures that the joint is filled to a desired degree.
In a common type of track assembly used in track-laying vehicles and crawler equipment, shoes of appropriate design are pivotally connected by hollow pins containing oil for lubricating opposing surfaces of the pins and surrounding bushings. A type of track known as Positive Pin Retention track was developed by the assignee of the present application to significantly reduce a common cause of lubrication loss in track joints. A pressed-in retaining ring is used to mechanically lock the pin and the link together. End play (sideways movement of the link) is minimized by the retaining ring which prevents relative motion between the link and pin during movement of the track. With essentially no end play, the seals maintain full compression against the ends of the bushings and retain oil in the joint cavities.
Upon initial assembly of the track, as well as in the course of maintenance and repair operations, it is necessary to fill the joint pins to a desired degree with lubricating oil and to ensure that the seals are intact, i.e., that there is no leakage. Leak testing is conventionally performed by applying a vacuum to the sealed area and testing for increases in pressure due to seal leakage. Because the volume of the oil reservoirs within the pins vary, it is not possible simply to place a uniform, measured volume of oil into each pin. In general, it is desirable to fill the pins to 80 to 90% of their capacity under a predetermined pressure which remains essentially constant over an extended period of track use. Presently used methods and apparatus for filling and leak testing track pin lubrication systems are inadequate to meet these desired standards. The present invention is directed to overcoming one or more of the problems or disadvantages associated with the prior art.
The apparatus of the invention includes a handle with an elongated nozzle or wand extending therefrom. The wand is dimensioned for insertion through a passageway in a seal in an undercarriage component. A first hose connects the nozzle, through pneumatically operated valves, to either a vacuum generator or a source of nitrogen at regulated pressure. The nozzle is also connected, through a second hose and pneumatically operated valves, to a source of lubricating oil. Pilot air for actuating the valves is supplied via corresponding solenoid valves which are connected, through appropriate switches, to electrical power. A transducer is mounted in the handle to measure barometric pressure and to measure back pressure of oil flow. The apparatus also includes a keypad having a plurality of function keys or buttons, as well as numeric buttons and indicator lights. To prepare the apparatus for performance of test and fill operations, with the handle resting in a holder attached to the oil tank, first and second buttons on the keypad are pushed to begin heating and circulating oil from the tank through the handle and back to the tank, and to turn on an electric motor connected to the oil pump. The transducer measures back pressure of the oil flow.
The successive steps in the method of the invention begin with measurement of barometric pressure in response to operator activation of a third button on the keypad. Measurement is performed by the handle-mounted transducer and stored in a Programmable Logic Controller (PLC) for use later in the fill cycle. This is followed by operator insertion of the wand into the track component reservoir through the normally plugged opening in the end seal. When the operator is ready for the test and fill cycle to begin, a switch on the handle is actuated, causing subsequent operations to be performed under control of the PLC. The first of such automatically controlled operations is causing nitrogen from the pressurized source to flow through vacuum and nitrogen lines, clearing them of foreign matter. A manually initiated purge of the nozzle is performed by pressing another of the keypad buttons before actuating the handle switch.
The handle is connected through the first hose, by actuation of pilot and pneumatic valves, to the pressurized nitrogen source until pressure within the joint cavity is 20 psi. After a wait of 10 seconds, pressure is again read by the transducer and conveyed to the PLC. If pressure has dropped less than 0.4 psi, seal integrity is acceptable, and communication of the handle through the first hose is switched from the nitrogen source to the vacuum generator. Pressure within the pin cavity is reduced until it reaches 15% of the barometric pressure previously read and stored in the PLC. Communication of the handle with the vacuum generator is then terminated and, by actuation of further solenoid-operated pilot valves and pneumatic valves, the handle is placed in communication, through the second hose, with the source of lubricating oil. Lubricating oil is then pumped to the component reservoir until the pressure reaches barometric plus back pressure, resulting in 80%-90% fill of the component.